1. Field of the Invention
This invention relates to semiconductor devices, and more particularly relates to a method of operating a non-volatile memory (NVM).
2. Description of the Related Art
Nonvolatile memory has been widely used in many electronic products, wherein the most populated non-volatile memory devices are those having a charge storage layer and being written and erased electrically, such as EEPROM and flash memory.
Such a non-volatile memory is formed based on a bulk semiconductor substrate conventionally, with the charge storage layer disposed between a control gate and the substrate. Recently, nonvolatile memory formed based on a thin semiconductor film with the thin- film transistor (TFT) technology has been provided, wherein each cell is a thin-film transistor. By utilizing the TFT technology, it is possible to repeatedly form a semiconductor film and a layer of TFT cells based thereon and thereby fabricate a 3D non-volatile memory array.
A non-volatile memory cell of TFT type is conventionally programmed through positive Fowler-Nordheim (+FN) electron tunneling into the charge storage layer and erased by ejecting electrons out of the charge storage layer. For the efficiency of +FN programming is lower, the programming time required is longer generating more heat. This makes the operating method unsuitable to a 3D non-volatile memory array because a 3D memory array particularly suffers from difficult heat dissipation in the prior art.